M. BECQUEREL ON CHEMICAL EFFECTS OF ELECTRICAL ACTION. 415 
it is obvious that metals can form, with their own solutions and pure 
or acidulated water, currents whose electrical action precipitates the 
metal. In this case there are two electrical effects: the one caused by 
the re-action of the two liquids one on the other; the second by the 
action of the acidulated water on the metallic plate; it is therefore a 
compound phenomenon, for the actions are added or subtracted ac- 
cording as they have the same or contrary directions. In the case under 
consideration the two actions are combined. Certain thermo-electrical 
phznomena and simple chemical actions ordinarily disengage electricity 
enough to produce decompositions resembling those just mentioned. 
Let us first direct our attention to the decompositions produced by 
thermo-electrical currents. 
2. Several experimentalists have tried to decompose water with thermo- 
electrical currents, but in vain; for in order to succeed, they should have 
experimented with salts decomposable by a weak current, such as ni- 
trate of silver and iodide of potassium, and disposed the apparatus so 
as to be able to determine the production of a new compound. 
Let us take two wires, the one of platina the other of copper, of a 
certain length and about 4 of a millimetre* in diameter; forming at 
one end of each wire a ring, and hook one ring on the other; the ring 
of the platina wire being very small, and that of the copper wire about 
three millimetres in diameter. If we solder the two rings, the cur- 
rent goes always in the same direction, from the platina to the copper, 
whether we heat the wire to the right or to the left of the points of junc- 
tion. Let us now solder a copper wire to the free end of the platina 
wire, after which burn a small quantity of sulphur upon the copper ring, 
and then place under the platina ring an alcohol lamp, so as to raise its 
temperature to red heat, keeping the copper ring as cool as possible, 
which may be done by placing the platina wire at the extremity of the 
white flame, so that this may be at very little distance from the copper 
ring. Now if we communicate the free ends of the copper wires with the 
ends of thé wire which forms the circuit of a galvanometer, we obtain a 
current of electricity of considerable energy passing from the platina to 
the copper. 
The copper ring is made larger than the other, so that it may be less 
heated when the temperature of the platina ring is raised to red heat. On 
the contrary, if we place the focal heat on the side of the copper wire, 
the electrical effects are reversed; and if we substitute in place of the 
platina wire another copper wire, the electrical effects will still be the 
same. But exposing the two rings to the same temperature, there will be 
no effect produced. The layer of sulphur with which the copper ring 
is covered sensibly augments the intensity of the current. 
Here then are two distinct electrical effects in a closed circuit, con- 
sisting of wires of two different metals, according as those wires are 
* 5 of a millimetre is about -, of an inch; 3 millimetres is about 4 of an inch. 
